Abstract: A position determining method and a work result management device. A position where work is done inside a space surrounded by surfaces is determined, wherein the position where work is done inside the space is a sidewall, wave receivers that receive an acoustic wave signal are placed at three or more points, which are on the same plane substantially parallel to the sidewall but not collinear with one another and whose position coordinates are known. The signal is transmitted from a wave transmitter that transmits an acoustic wave and is placed at the position on the sidewall where work is done, and the respective arrival times of the signal at the three or more wave receivers that are not collinear with one another are measured to determine the position coordinates of the wave transmitter using the arrival times and the position coordinates of the three or more wave receivers.

Abstract: To provide a position determining method and a work result management device, used for internal inspection of a space surrounded by surfaces such as a boiler furnace, and further used for inspection of an inner or outer wall in a vessel and capable of detecting plural positions.